A Near-Infrared Cationic Photosensitizer for Lysosomal Activated Tumor Imaging and Photodynamic Therapy

The process of photodynamic therapy (PDT) is to use specific light irradiation to excite a photosensitizer (PS) to generate reactive oxygen species (ROS) to kill tumor cells. Traditional photosensitizers (PSs) have the problems of poor tumor imaging and low ROS generation efficiency. The cationic photosensitizer TBZTI based on the D-π–A structure exhibits near-infrared fluorescence emission (730 nm) and a large Stokes shift (180 nm). TBZTI can be effectively aggregated into nanoparticles (100 nm) in aqueous solution, which are always in a fluorescence-off state. TBZTI can target lysosomes and be activated in a fluorescence-on state for high signal-to-noise ratio tumor imaging. TBZTI has low cytotoxicity, good biocompatibility, and high singlet oxygen generation efficiency (6.4-fold that of Rose Bengal). Cytotoxicity and apoptosis experiments further demonstrate that TBZTI can effectively kill cells and induce apoptosis under white light. TBZTI has a significant effect on PDT in mouse tumors, which obviously inhibits tumor growth and triggers the apoptosis of tumor cells. This work provides an important reference for the design and synthesis of photosensitizers with activated fluorescence, high singlet oxygen generation efficiency, and high signal-to-noise ratio tumor imaging.